FURTHER TARGET DATA options

In order to access these options you should select the EXPERT
OPTIONS sheet (close to the upper left corner of the main program
window).

There are two options to modify the target specification:

USE OSCILLATOR STRENGTHS option

GAS TARGET option

USE OSCILLATOR STRENGTHS option

Without selecting this option, the whole spectrum of
dipole-oscillator strengths for low electronic energy transfers is
replaced by a single (representative) oscillator for each target
subshell. The corresponding energy transfer summed over all shells is
given by the mean target-ionization potential I_Bethe, similar
as in the simple Bethe formula. A proportionality between oscillator
energy and binding energy is assumed for the distribution of the
oscillator energies over all electronic shells.

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This option is provided for advanced users only.

When selecting this option, a popup-window will ask for the
directory and for the name of an ASCII file containing numerical
OSCILLATOR STRENGTHS for the target K-shell. The name of this file must
be “Osc1.dat”. The names Osc2.dat, Osc3.dat, and so forth
are reserved for the other shells (2s, 2p, …). It is recommended
to use a separate subdirectory for each target system and to store all
the corresponding “Osc*.dat” files in these directories.

Each of the files must contain a list of oscillator strengths (a
single line for each transition) in an ascending order of the energy.
For each transition, the final-state energy has to be given first (in
atomic units, 1 a.u.=27.2 eV) and the corresponding oscillator strength
as a second parameter (also in atomic units). For continuum states the
oscillator strengths have to be integrated over the energy bin,
corresponding to the specific continuum energies. Internally, CasP will
just sum over all oscillator strengths (no advanced integration or
extrapolation is performed here).

Note that one sample file “Osc1.dat” is included
within this package. This file contains numerical oscillator strengths
for the hydrogen atom and should be stored in the subdirectory
“OscH”. Another set of sample files “Osc1.dat”
to “Osc3.dat” for carbon, calculated from
Hartree-Fock-Slater wave functions, should be stored in the
subdirectory “OscC”. For intermediate and especially for
large impact parameters, the use of numerical oscillator strengths
improves the results. For many atoms, numerical values or fits to
dipole-oscillator strengths may be found in the literature.

GAS TARGET option

Without selecting this check box, the target is assumed to be an amorphous solid
or a liquid of similar target density (otherwise a low density gas target).
This option will only influence the mean projectile charge state
(for pure elements as well as also for the compound targets).